The use of fluid pressure, whether in the form of a vacuum below atmospheric pressure or in the form of a positive pressure above atmospheric pressure has long been known in the prior art for controlling various devices. Many devices for regulating fluids at vacuum or at positive pressures is likewise known to the art. Generally such fluid pressure regulators have been controlled in the past either manually or in response to some type of electrical, mechanical or fluid signal that conveys some type of a command to the regulator. Additionally, changes in parameters such as temperature, pressure and fluid flow have been commonly used in the past as a means of causing a change in the regulation of fluid pressure so as to commence some corrective function to dampen or eliminate the change.
The concept of using changes in rotational speed is particularly useful for controlling various accessories associated with motor vehicle engines since in many instances a rotating component of the engine can be readily monitored for changes and the engine itself can be used to drive an air compressor or vacuum pump to provide the fluid pressure supply for use by a fluid pressure regulator to provide the fluid pressure control signal to control the particular accessory. Motor vehicle accessories that can be adapted to be controlled by fluid pressure signals include, pollution control devices, vacuum tachometers, cruise control, transmission shifting mechanisms and for clutching and de-clutching accessories such as compressors, alternators and the like as well as controlling or otherwise monitoring such operating conditions as, for example, the engine idling speed or coolant fluid temperature.
Of particular interest is the use of a change in the rotational speed of an engine as a means of controlling a supercharger for boosting air intake into the engine at a predetermined engine speed so as not to burden the engine with the load of the supercharger when the engine is idling. Also of interest in controlling the supercharger of an engine is the use of changes in at least one additional engine operating condition such as the throttle position, altitude, coolant temperature and the like in combination with a change in the engine rotational speed in such a manner that the combination is able to regulate a fluid pressure regulator to provide a fluid pressure control signal that is able to effectively control the supercharger.
An example of one type of mechanism that utilizes a governor to provide a cruise control for controlling the speed of a motor vehicle is disclosed in U.S. Pat. No. 3,298,482. The mechanism however incorporates a complex combination of mechanical and electro-mechanical components and is not able to utilize the governor in a simple manner to provide a fluid pressure control signal that is highly sensitive to changes in the rotational speed of the object being monitored by the mechanism and is susceptible to high maintenance expenses.
In view then of the many applications for which changes in rotational speed of an object may be effectively used singularly or in combination with one or more other fluid pressure signals for use in control functions, a need exists to provide a mechanism that is simple in construction and is easily maintained at minimal expense while being able to provide a fluid pressure signal that is highly sensitive to changes in the rotational speed of an object being monitored by the mechanism.